This invention relates to the construction of radiation imaging systems, as well as other systems providing for the amplification of low level signals, such as systems employing cryogenic apparatus and, more particularly, to the construction of a set of amplifiers and systems employing the amplifiers wherein each amplifier is formed of stages powered by electric energy stored in capacitors.
A situation of particular interest in the amplification of small signals is found in the amplification of a set of signals obtained from an array of radiation detectors, such as an array of infrared (IR) semiconductor detectors employed in an imaging system. Such an imaging system may be used in radio astronomy. The faint signals of distant sources of radiation are focused by an optical unit upon the detectors located at a focal plane of the optical unit for detection of the signals, and are amplified by semiconductor amplifiers coupled to respective ones of the detectors. It is common practice to mount the detectors in a cold compartment located behind the optical unit to reduce the presence of noise. The detectors are cooled cryogenically. It is also advantageous to operate the amplifiers at cryogenic temperatures to reduce the generation of noise by the amplifiers. A problem arises in that currently available amplifiers for amplification of the detector signals dissipate more power than is desireable, thereby creating a burden of heat removal for cryogenic equipment. In addition, such amplifiers do not readily permit correction of nonuniformity in the responsivities of the individual detectors at the focal plane so as to simplify subsequent signal processing, and may lack a desired degree of radiation hardness.